Evolution of microRNA genes in Oryza sativa and Arabidopsis thaliana: an update of the inverted duplication model

The origin and evolution of microRNA (miRNA) genes, which are of significance in tuning and buffering gene expressions in a number of critical cellular processes, have long attracted evolutionary biologists. However, genome-wide perspectives on their origins, potential mechanisms of their de novo generation and subsequent evolution remain largely unsolved in flowering plants. Here, genome-wide analyses of Oryza sativa and Arabidopsis thaliana revealed apparently divergent patterns of miRNA gene origins. A large proportion of miRNA genes in O. sativa were TE-related and MITE-related miRNAs in particular, whereas the fraction of these miRNA genes much decreased in A. thaliana. Our results show that the majority of TE-related and pseudogene-related miRNA genes have originated through inverted duplication instead of segmental or tandem duplication events. Based on the presented findings, we hypothesize and illustrate the four likely molecular mechanisms to de novo generate novel miRNA genes from TEs and pseudogenes. Our rice genome analysis demonstrates that non-MITEs and MITEs mediated inverted duplications have played different roles in de novo generating miRNA genes. It is confirmed that the previously proposed inverted duplication model may give explanations for non-MITEs mediated duplication events. However, many other miRNA genes, known from the earlier proposed model, were rather arisen from MITE transpositions into target genes to yield binding sites. We further investigated evolutionary processes spawned from de novo generated to maturely-formed miRNA genes and their regulatory systems. We found that miRNAs increase the tunability of some gene regulatory systems with low gene copy numbers. The results also suggest that gene balance effects may have largely contributed to the evolution of miRNA regulatory systems.     

达尔文-科学进化论的奠基者

2009年, 时逢英国博物学家查尔斯·罗伯特·达尔文(Charles Robert Darwin,1809-1882)诞辰200周年, 进化论光辉著作《物种起源》发表150周年。历史的发展不断认证达尔文的《物种起源》一书是生物学史上不朽的经典著作, 如今《物种起源》所提及的许多观点已成为人尽皆知的常识, 并且还在不断地发展、完善, 为人类认识自然和自身发展指点方向。文章追忆了先贤的卓越科学贡献和科学探索精神, 并对百年来科学进步和进化论的发展重要成果进行了简要的评述, 指出了进化论未来研究的重点问题。     

Molecular cloning, prokaryotic expression and expression at different developmental stages of cathepsin B gene in mealybug Phenacoccus solenopsis Tinsley ( Hemiptera: Pseudococcidae)

昆虫组织蛋白酶B在昆虫代谢过程中发挥重要作用.本研究利用RACE技术克隆了扶桑绵粉蚧Phenacoccus solenopsis Tinsley组织蛋白酶B基因的开放阅读框(ORF)序列,命名为PsCb(GenBank登录号:JQ727999).生物信息学分析表明,该基因的开放阅读框包含927 bp的片段,编码308个氨基酸.多序列比对表明,该基因编码的蛋白在N端变异较大,在C端保守性高.组织蛋白酶B基因的系统进化树结果表明扶桑绵粉蚧组织蛋白酶独自成为一支.原核表达电泳检测到一条大约35 kDa的目的条带,与预测的蛋白分子量相符.组织蛋白酶B基因在扶桑绵粉蚧各个虫态均有表达,卵期表达量相对较低,2龄若虫期达到最高峰,然后下降.本研究为进一步研究该基因的功能并开发出组织蛋白酶抑制剂,从而研制出扶桑绵粉蚧杀卵剂和胚胎发育抑制剂等提供理论依据.     

家鸽臂丛和坐骨神经传入冲动在纹状体的投射

在53只家鸽的纹状体上系统地探查了刺激臂丛和坐骨神经所引起的平均诱发电位。结果发现,臂丛传入的投射区位于新纹状体、上纹状体和外纹状体之内,坐骨神经传入投射区则分别与臂丛传入的新纹状体投射区和上纹状体部分投射区重合;臂丛和坐骨神经投射区均接受身体两侧的传入。作者认为,家鸽纹状体内的前、后肢躯体感觉传入投射区是分散的,并非形成一个集中的中枢;前肢的投射区较大,可能与机能分化有关,身体不同部位的传入冲动在同一投射区内的会聚,对于肢体活动的整合具有重要意义。     

猫颈部和腹部迷走神经加压反应的比较研究

刺激麻醉猫颈部和腹部迷走神经中枢端引起的升压反应,不但反应模式有别,其升压机制也不同。颈部迷走加压反应是在出现快速降压之后的一个缓慢持续的血压升高,而腹部迷走加压反应则是一个快而短暂的升压反应。在颈迷走加压反应出现的同时伴有血浆加压素(AVP)的增加,但血浆肾素活性(PRA)及血管紧张素 Ⅱ(ANG Ⅱ)和肾神经放电(RND)都有不同程度的下降。腹部迷走加压反应的出现则伴有 RND,PRA 和血浆 ANG Ⅱ 水平的增加,但 AVP 无明显改变。兴奋同一迷走神经颈腹段传入纤维引起的升压效应之所以不同主要是由于传入纤维的来源和在中枢的投射部位不同,因而升压机制也各异。     

Assembly of lamins in vitro

After lamins A,B and C were isolated and purified from rat liver,their assembly properties were examined by electron microscopy and scanning tunneling microscopy by electron microscopy and scanning tunneling microscopy using negative staining and the glycerol coating method,respectively.By varying the assembly time or the ionic conditions under which polymerization takes place,we have observed different stages of lamin assembly,which may provide clues on the structure of the 10 nm lamin filaments.At the first level of structural organization,two lamin polypeptides associate laterally into dimers with the two domains being parallel and in register.At the second level of structural organization,two dimers associate in a half-staggered and antiparallel fashion to form a tetramer 75 nm in length.At the third level of structural organization,4-10 lamin tetramers associate laterally in register to form 75 nm long 10nm filaments,which in turn combine head to head into long,fully assembled lamin filaments.The assembled lamin filaments are nonpolar.     

裸子植物上的三个小煤炱科新种

本文报道寄生在裸子植物上的三个小煤炱科新种。它们是(1)杉科上的杉木附丝壳Appendiculella cunninghamiae Y.X.Hu et B.Song,杉科是小煤炱科寄主的世界新记录;(2)罗汉松科上的竹柏生小煤炱Meliola podocarpicola Y.X.Hu et B.Song;(3)买麻藤科上的买麻藤生小煤炱Meliola gneticola Y.X.Hu。其形态特征有拉丁文和汉文描述,并附有形态图。模式标本存放在广东省微生物研究所。     

脑室注射NE对室旁核神经内分泌大细胞的作用

在成年ＳＤ大鼠上,用玻璃微电极进行细胞外记录,结合逆行鉴定技术确定下丘脑室旁核神经内分泌大细胞,并观察其对去甲肾上腺素的反应。在４９个逆行鉴定神经元中,位相型,快连续型及慢不规则型放电单位分别占４２．９％,３６．７％及２０．４％。脑室内注射去甲肾上腺素（０．２μｇ／μｌ）对位相型单位主要产生抑制作用,对快连续及慢不规则单位主要为兴奋作用。脑室内注射酚妥拉明（２μｇ／μｌ）能部分拮抗ＮＥ对位相型神经元的抑制。结果表明：ＮＥ对室旁核中不同类型放电单位作用不同,其对位相型单位抑制作用可能由α受体参与介导。     

DIFFERENTIAL THRESHOLD AND PSYCHOPHYSICAL POWER FUNCTION OF SWEETNESS SENSATION: APPLIED PSYCHOPHYSICS AND PROSPECT THEORY ON FORMULATING BAKING PRODUCTS

The main purpose of this project was to develop the optimal sweetness sensation framework for baking products. Phase 1 was designed to measure consumers' differential thresholds of sweetness sensation when the sweetener contents of various sweetener‐leveled products were increased and lowered by using the constant stimuli method. Results indicated that the consumers' differential thresholds increased when the initial sweetener levels of products increased. Phase 2 was designed to establish the psychophysical power function of sweetener‐content changes and consumers' psychological sensation of products with different sweetener levels by adopting the magnitude estimation method. Regardless of the initial sweetener levels of products, the results showed that consumers perceived the products as less sweet immediately after the sweetener contents of products dropped by even a small amount; however, consumers perceived products as sweeter only when products dramatically increased in contents of sweetener.     

60Co辐射诱变对巴氏蘑菇(姬松茸)子实体多糖组分与结构变化的影响

巴氏蘑菇(姬松茸)原菌株J1和辐射突变株J3子实体粗多糖经水提、醇沉、Sevage法去除蛋白,透析得精多糖ABJ-1和ABJ-3;经紫外扫描和凝胶色谱法检测表明,ABJ-1和ABJ-3均具有较高的纯度。以苯酚-硫酸法测得了ABJ-1和ABJ-3的糖含量分别为47%和76.68%,凯氏定氮法测定其含氮量分别为5.77%和21%。,以凝胶过滤法测定了其分子量均在4万左右。完全酸水解后气相色谱分析显示ABJ-1含有甘露糖、葡萄糖、半乳糖等单糖,ABJ-3含有大量的甘露糖及少量的葡萄糖等单糖。红外光谱和Smith降解后气相色谱分析显示ABJ-1和ABJ-3糖基连接键均以a,1-4糖苷键为主。